Greg has done one PFM retip that in know of for sure since he posted about it on his blog a few years back. It sounded a bit tricky because of the heat as noted but I do remember actually seeing that he did one.
With this thread in mind I specifically asked him about the nibs the other day, so the information is current. If he did them, I would offer that as an option to clients with a bad FPM nib. Some day the supply of replacement nibs will dry up.